Webroot has "decided to break the cord with signature-based AV," said Brian Czarny, vice president of product management. Many antivirus programs still rely in part on systems that require identification of a piece of malware, which is then further identified by security products once a "signature" is pushed to a PC's security application.

But most security experts agree that signature-based detection is fairly ineffective these days due to the sheer number of malicious software samples that are created and the clever ways those applications are manipulated in order to evade security software. Czarny said Webroot was detecting about 40,000 pieces of new malware a day in 2009; these days, the figure is around 100,000 daily.

Webroot's SecureAnywhere doesn't rely on signatures anymore. SecureAnywhere downloads a very small client to a PC -- less than 1MB -- which then communicates with Webroot's database of known malware, as well as back-end systems that perform behavioral analysis of suspicious programs.

The result is a security application that has a very low footprint and doesn't hamper the computer's overall performance. SecureAnywhere does an initial scan, which takes a few minutes, but subsequent scans take much less time since they only look at modified or new programs.

If a suspicious program is downloaded to a machine, SecureAnywhere allows it to execute on the computer, Czarny said. But it does this by wrapping a "pseudo sandbox" around the browser, which prevents the malware from doing any harm, he said.

While the program is executing, SecureAnywhere looks at its behavioral characteristics as well as comparing it to known malware in Webroot's data center. If it's bad, the program gets blocked, and SecureAnywhere wipes it from the PC, Czarny said.

The small client on the PC also contains a set of rules in case a computer is offline. For example, if a person is offline but inserts a USB stick with a malicious application, it will execute in the sandbox and its behavior is logged. When the computer reconnects, SecureAnywhere checks the database to see if it is bad. If so, it's cleaned from the machine.

SecureAnywhere comes in three different versions: a basic "Antivirus," which costs $39.95 for one PC or $49.95 for three licenses. A next version, "Essentials," includes features such as a cloud-connected firewall, antiphishing, and 2GB per user of online file storage. Essentials costs $59.95 for three licenses.

The high-end product, "Complete," ups online storage to 10GB per user, plus adds other features such as password and personal identity management tools, file and password sync with mobile devices. That version retails for $79.95 for three PCs and three mobile devices, according to Webroot.